Automatic gripping means for machine tools and the like



Aug. 17, 1954 1 CSAK| 2,686,682

AUTOMATIC GRIPPING MEANS FOR MACHINE TOOLS AND THE LIKE Filed July 8, 1952,"

l l I l l l I l 135 132 15 134 112 17 16 18 I INVEHTORZ. TOACHIM CSAK] VPatented Aug. 17, 1954 AUTOMATIC GRIPPING MEANS FOR MACHINE TOOLS AND THE LIKE Joachim Csaki, Stuttgart, Germany Application July 8, 1952, Serial No. 297,695

14 Claims.

The present invention relates to automatic gripping means for machine tools and the like.

More particularly, the present invention relates to chucks of the collet type which are axially movable in a spindle between gripping and releasing positions, these collets usually having slotted outer ends providing springy tongues, and these tongues having a beveled outer surface engaging a conical surface on the spindle to produce the gripping and releasing action of the collet upon axial movement thereof in the spindle.

In most machine tools, and in particular on portable machine toools, such as portable grinding machines, for example, such collets are axially moving through manually operable means which require the spindle to be held stationary by pin members or the like which extend through transverse openings of the outer casing. Such devices are extremely inconvenient and do not always produce the desired gripping action.

One of the objects of the present invention is to overcome the above disadvantage by providing a means for operating the collet in a fully automatic manner.

A further object of the present invention is to provide a means actuated by the centrifugal force of a rotating spindle for operating a collet.

Another object of the present invention is to provide a means for holding an article in a collet before the article is gripped by the collet.

A still further object of the present invention is to provide an apparatus capable of accomplishing all of the above objects while at the same time being made of few, simply and ruggedly constructed parts which are very reliable in operation.

With the above objects in view the present invention mainly consists of a gripping apparatus associated with a hollow rotatable machine spindle. This gripping apparatus includes a gripping member, such as a collet, mounted in the spindle for axial movement therealong between a gripping and a releasing position. A moving member is located in the spindle for automatic movement, by centrifugal force produced by the rotating spindle, between a rest position, when the spindle is stationary, and an operating position, when the spindle rotates, this moving member being operatively connected to the gripping member for moving the same from the releasing to the gripping position thereof upon movement of the moving member from the rest to the operating position thereof, so that an article placed within the gripping member will 2 be automatically gripped upon rotation of said spindle.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. l is a fragmentary side sectional view of a machine part having the structure of the invention associated therewith;

Fig. 2 is a sectional view of a part of the structure of Fig. 1 taken along line A--B of Fig. 1 in the direction of the arrows; and

Fig. 3 is a side sectional View, similar to Fig. l, of a different embodiment of the present invention.

Referring now to the drawings, the apparatus illustrated in Fig. l includes a collet I0 which, at its right hand end, is formed with inwardly extending slots to provide tongues |0| having outer conical surfaces engaging a corresponding conical seat of the rotating spindle I I. The collet I 0 is slidably mounted in a hollow free end portion ||2 of the spindle The inner end of the collet I0 is threadedly connected to a bolt I2 whose head |2| is formed as a flat piece guided in a slot ||3 passing transversely through the spindle II.

In this slot ||3 are loosely located a pair of nat, hook-shaped members I3 having shorter legs I 3| which engage the shoulder of the flat screw head |2I, and, in their rest position, the longer legs |32 of the members I3 have their inner edges parallel to the spindle axis, as illustrated in Fig. 1. In order to prevent these longer legs |32 from crossing over the spindle axis and interfering with each other, a transverse bolt I4 is mounted within the spindle, and the longer legs |32 are provided with cut-outs |33 engaging the bolt ||4 when the spindle is stationary. The members I3 are provided with outer curved edge portions |34 at the junction between the legs I3| and 32 thereof, and these curved edge portions |34 engage an inner part o-f a member I5 connected to the spindle I for rotation therewith in such a way that the members I3 can turn in their own plane while bearing against an annular surface portion on the inside of this member I5, as. illustrated in Fig. 1.

`The spindle II is mounted rotatably in a casing Il by means of the roller bearing i6. This bearing i6 is maintained in a predetermined axial position by the sealing means i8 against which a nut i9 bears, this nut I9 being threadedly connected to the hollow casing Ily as illustrated at the right-hand part of Fig. l.

In Fig. l the moving members i3 are shown, in solid lines, in their rest position. When an article such as the shank of a tool, for example, is placed within the collet le and the spindle is set into rotation, then when a sufficient speed of rotation has been attained the longer and heavier legs l32 of the members I3 move, by centrifugal force, out of the slot H3 of the spindle il. These members I3 turn about the curved edges i3d thereof. This causes a movement o1" the shorter legs |34 inwardly into the casing il and, by engagement with the shoulders of bolt head 12d, legs iti move the collet Ill inwardly into the spindle Il. Thus, the conical seat HI presses against the tongues lili to cause the latter to tightly grip an article located Within collet I0. The annular member i is formed to simultaneously serve as a stop for limiting the turning of the moving members i3 under centrifugal force, these members i3 being movable to the dotted line position illustrated in Fig. l.

Since the operation of the apparatus is dependent upon a minimum speed of rotation, the above described apparatus is capable of acting as a safety device against overloads, because when the load increases the speed of rotation decreases, and when this speed of rotation becomes too small to provide the automatic gripping force by centrifugal action, the tool or the like located within the collet becomes free and can then turn within the opening of the collet.

In order to prevent an article placed within the collet it from falling out of the same when the spindle is stationary, there is provided, in accordance with the present invention, a device for holding such an article within the stationary collet. One example of such a device is shown in Fig. 2 where it is seen that a springy arcuate member lb? passes about and engages the collet Hi and is provided with a bent free end portion extending radially through one of the slots W3 of the collet l@ into the interior of the inner space of the collet il?. Thus, when an article is placed within the collet. lli, this article engages the yieldable free end of member It? located in the interior of the collet it so as to be yieldably pushed by this free end of member It?. against the inner surface of the collet Ill and thereby frictionally held within the latter with a light pressure.

In the example of Fig. 3, there is provided a bearing support 2l in which a spindle 2l is located and rotatably mounted by the ball bearing 25. This ball bearing is held in position by the sealing ring 28 and outwardly threaded collar 29 which threadedly engages an inner portion of the bearing support 2l. This bearing support 2l Vis located within the casing Sil. The outer enlarged end 2 lll of the spindle 2l is formed with a transverse slot 2li and is threaded at its outer end 2li. To this threaded part 2H of spindle 2l there is connected a member 3l provided with an inner conical surface for engaging the tongues oi collet 2li. This collet is set into the central bore 2l? of spindle 2i and is moved to the right, as viewed in Fig. 3, into its gripping position by engagement of its tongues with the inner conical surface of member 3l. This movement of collet 2@ into its gripping position is accomplished 4 through the medium of hook-shaped members 23 which are flat and located within the slot 2H, these members 23 having shorter legs 23! located against the rear end of collet 2b. In 'the rest position of the apparatus, the members 23 assume the position shown in solid lines in Fig. 3, where their longer legs 232 extend in a direction substantially parallel to the spindle axis. Upon rotation of the spindle, the members 23 turn to the dotted line position illustrated in Fig. 3, the members E3 turning about their edge portions 234 which rest against a ring-shaped part 2id fixed on the enlarged spindle part 2id. In order to limit the outward movement of legs 232 of members 23, the spindle part 2 It has iixedly mounted thereon an additional ring-shaped member 32 which extends over the free ends of legs 232 so that the latter engage member 32 when moving away from the spindle by centrifugal force upon rotation of the spindle.

Upon 'turning of the hook-shapedmembers 23 under centrifugal force as described above, their shorter legs 23| push against the free inner end of the collet 2!) and move the latter to the right,

as viewed in Fig. 3, so that a gripping action is automatically provided.

It should be noted that with the above described structure it is unnecessary to provide in member Il or 3G a hole adapted to receive a locking pin for holding the spindle stationary, e. g., While tools are being gripped or released. Since no interior locking mechanism is required in the structure according tothe invention the member Il or 3l) may be of a more compact shape as compared with corresponding parts in known devices, as it is clearlyA evident from'the righthand portions of Figs. l and 3. Thus, when a small-size grinding wheel is attached to an apparatus, such as that of `Fig. l or 3, it will be possible to hold the device according to the invention in such a manner that the angle between its axis and the surface to be ground is extremely small, whereby the grinding action is materially improved. Expressed in a different manner, while grinding with a small-size grinding wheel may only be achieved with a conventional device when the latter is held with its axis at a considerable angle to the surface to be groundan operation whichv has evidently decided drawbacksthis is not necessary when grinding with ardevice according to the invention where the small diameter of the structure or practically the same order-at least atits end Yportion-as the grinding wheel allows of applying the wheel with its axis almost parallel to the surface to be ground. Y A

It will be understood that each of the elements described above, or two or more together, may also nd a useful application in other types ci automatic gripping means for machine tools and the like, diiering from the types described above.

While the invention has been illustrated and described as embodied in centrifugal automatic gripping means for machine tools and the like, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departingin any way from the spirit of the p-res-ent invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge` readily adapt it for various applications without omitting features that, from the standpoint of invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. In a machine tool or the like, in combination, a spindle adapted to rotate, having a hollow end portion and being formed with a radial slot communicating with the interior of the hollow end portion of said spindle; a collet mounted in said hollow end portion of said spindle for axial movement between an expanded position, where articles may be removed from and placed into the collet, and a contracted position gripping an article in the collet; an actuating member fixed to said colletI and located within said spindle, so that said collet will move axially in said spindle upon axial movement of said actuating member; a moving member located in said slot for free turning movement about an axis perpendicular to the spindle axis, said moving member having a first portion engaging said actuating member, for moving the same and said collet therewith, and a weight portion freely mounted in said slot for movement by centrifugal force substantially radially away from the spindle axis upon rotation of said spindle, said movement of said weight portion moving said engaging portion to thereby move said actuating member and collet therewith, so that said collet automatically grips an article located therein upon rotation of said spindle; and a tubular housing located about said spindle and collet and completely enclosing said actuating member and said moving member'.

2. In a machme tool or the like as defined in claim 1, stop means located in said housing on said spindle adjacent to said moving member for limiting the turning movement of the same upon rotation of the spindle.

3. In a machine tool or the like as defined in claim l, a springy member mounted on said collet and having a free end portion extending into the interior of the latter so that said free end portion of said springy member is yieldably movable outwardly of the interior of the collet whereby an article placed in the collet while the latter is stationary will be frictionally engaged by said free end portion of said springy member to be maintained in the stationary collet.

4. In a machine tool or the like as defined in claim 3, said collet being formed with a plurality of radial slots and said springy member having an arcuate portion located about and engaging said collet over said slots thereof and said free end portion of said springy member being bent from said arcuate portion and extending through one of said radial collet slots into the interior of said collet.

5. In a machine tool or the like, in combination, a spindle turnably mounted for rotation about its axis and having a hollow end portion, said spindle being formed with a radial slot communicating with the interior of said hollow end portion of said spindle; a collet slidably mounted in said hollow end portion for axial movement between gripping and releasing positions, said collet having an outer end portion adapted to grip an article placed in said collet and an inner end portion located within said hollow end portion of said spindle; a substantially hookshaped moving member located within said slot of said spindle for turning movement about an 6A axis perpendicular to the spindle axis and in a plane including the latter, said moving member having one leg engaging said inner end portion of said collet and another leg freely movable in said slot, so that when the spindle :is rotated said other leg of said moving member will move by centrifugal force substantially radially away from the spindle axis to cause said one leg of said moving member to move said collet into the gripping position thereof.

6. In a machine tool or the like, as deiined in claim 5, said other leg of said moving member being heavier than said one leg thereof.

'7. In a machine tool or the like, as defined in claim 5, said other of said moving member being longer than said one leg thereof.

3. In a machine tool or the like, in combination, a rotatable spindle having a hollow free end portion and being formed with a radial slot communicating with the interior of said hollow spindle end portion and having a shoulder facing in a direction away from the outer extremity of said free end portion of said spindle; a collet slidably mounted in said hollow free end portion of said spindle for movement outwardly of said spindle into a releasing position and inwardly into said spindle to a gripping position; a rigid member xed to the inner end of said collet within said spindle and having a shoulder facing said outer extremity of said spindle; and a substantially hook-shaped moving member havling a pair of legs forming a curved portion on said moving member, the latter being located in said slot with said curved portion of said moving member bearing against said shoulder of said slot, one of said legs of said moving member engaging `said shoulder of said rigid member so that upon rotation of the spindle the other of said legs of said moving member moves in a substantially radial direction away from the spindle axis to cause said moving member to turn on said slot shoulder about the curved portion of said moving member and to thereby cause said one leg of said moving member engaging said shoulder of said rigid member to move said rigid member and collet therewith inwardly into said hollow free end portion of said spindle so as to automatically cause said collet to grip an article located therein.

9. In a machine tool or the like, in combination, a rotatable Spindle having a hollow, free end portion and being formed with a radial slot communicating with the interior of the hollow spindle end portion and having a shoulder facing toward the outer extremity of said free end portion of said spindle; a collet slidably mounted in said hollow free end portion of said spindle for movement outwardly of said spindle into a gripping position and inwardly into said spindle to a releasing position, said collet having a free inner end located within said hollow spindle end portion; and a substantially hook-shaped moving member having a pair of legs forming a curved portion on said moving member, the latter being located in said slot with said curved portion of said moving member bearing against said shoulder of said slot, one of said legs of said moving member engaging said free inner end of said collet so that upon rotation of the spindle the other of said legs of said moving member moves by centrifugal force in a substantially radial direction away from the spindle axis to cause said moving member to turn on said slot shoulder about the curved portion of said moving member and to thereby cause said one leg of said moving member engaging said free inner end of said collet to move the latter outwardly of said spindle so as to automatically cause said Collet to grip an article located therein.

10. In a machine tool, in combination, a rotatable spindle having a hollow free end portion; collet means slidably mounted on said spindle end portion for axial movement between gripping and releasing positions; and a pair of moving members symmetrically mounted in said spindle end portion for free turning movement about parallel axes, respectively, perpendicular to the spindle axis, each of said moving members having one leg engaging said collet means and another free leg movable by centrifugal force in a substantially radial direction away from the spindle axis upon rotation of the latter to cause said one leg thereof to engage said collet means and move the same into the gripping position thereof.

11. In a machine tool asdeiined in claim 10, said other legs of said moving members being substantially parallel to each other and to the spindle axis when the latter is stationary.

12. In a machine tool as defined in claim 11, stop means located on said spindle opposite said other legs oi said moving members to limit the outward movement thereof upon rotation oi said spindle.

13. In a machine tool as defined in claim 12, limiting means located in said spindle between said other legs of said moving members for limiting the movement of said other legs toward the spindle axis when said spindle is stationary.

14. In a machine tool, in combination, an elongated spindle adapted to rotate about its axis, said spindle having a hollow free end portion and being iormed with a radial slot communicating with the interior of said hollow end portion of l said spindle; a collet mounted in said hollow end portion of said spindle for movement toward one end of said spindle into an expanded position, where articles may be removed from and placed into the collet, and toward an opposite end of said spindle into a contracted position gripping an article in the collet, an actuating member fixed to said collet, so that the latter moves upon movement of said actuating member, and having a face directed toward said one end oi said spindle; a member xed to said spindle for rotation therewith and having a curved shoulder located opposite said slot and being directed toward said opposite end of said spindle; and a flat, substantially hook-shaped moving member freely located at least partly within said slot, having one leg engaging said face of said spindle and a second leg larger than said one leg and extending from said one leg toward said opposite end of said spindle, said member being provided at the junction between said legs with a curved portion located against said curved shoulder so that said curved portion and said shoulder cooperate to form a pivot axis about which said moving member turns by centrifugal force, upon rotation or said spindle, to automatically move said collet toward the opposite end oi said spindle into a gripping position.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 594,077 Gauthier Nov. 23, 1897 1,990,525 Chancellor Feb. 12, 1935 FOREIGN PATENTS Number Country Date 481,505 France 1916 

